El Niño, part II: Global & local effects / MWN Winter Outlook

In part 1 of this blog series on El Niño, we examined the basics of ENSO (El Niño Southern Oscillation), including what exactly it is and how ocean temperatures affect global weather patterns, a little history as to how it was discovered, and how it is measured. In this final installment, we examine the typical effects of El Niño globally, as well as what we have experienced locally in prior El Niño years, and finally what we might expect this winter. This blog will also serve as the "2015-'16 MWN Winter Outlook" post that is commonly requested this time of year.

Global effects of El Niño

Though effects on the atmosphere over North America, and the rest of the world, vary with each El Niño, there are some typical atmospheric responses. The effects are most visible during the winter months, since that is when the waters of the Pacific tend to be warmest during El Niño years, and include:

• Increased precipitation across the southern tier of the U.S, including drought-stricken California, due to a more active Pacific jet stream
• Decreased precipitation across the Pacific Northwest and Ohio Valley
• Warmer than average conditions across the northern half of the U.S. and southern Canada, as the polar jet stream is displaced further north
• More coastal storms affecting the eastern U.S., and
• In summer, suppressed activity in the tropical Atlantic and increased activity in the eastern Pacific.

Below are the typical El Niño patterns during the winter (top) and summer (bottom) months globally. These "typical" effects are often be offset by other, shorter-term, regional or global patterns that are much less predictable beyond a couple of weeks. For instance, just because a region is usually dry or cool doesn't mean the entire winter will fall into that pattern.

Regional effects of El Niño

Mid-South weather can be fairly fickle during El Niño winters, as we are typically positioned between the persistent Pacific jet stream that brings wet and cool conditions to the southern U.S. and a pronounced dry area over the Ohio River Valley, which can extend as far south of the Tennessee River Valley. If either of those areas shifts slightly due to other variables, Mid-South weather could end up either wetter or drier than average, particularly for short durations over the course of the winter.

Mid-South temperatures over the course of an El Niño winter are generally driven by shorter-term regional variations that occur. El Niño itself generally places us in a "near average" temperature regime, between cooler than average weather to the south (nearer the Pacific jet stream) and warmer than normal weather to the north.

Typical climate pattern over North America during El Niño winters. Graphic courtesy NOAA/CPC.

Other factors: Teleconnections

While El Niño will be the primary factor on our winter weather pattern, there are other climate influences (or "teleconnections") that may last only for a week or two at a time that frequently determine local weather conditions. These are much less predictable more than a couple of weeks in advance. These include the North Atlantic Oscillation (NAO), Arctic Oscillation (AO), Pacific Decadal Oscillation (PDO), Pacific-North American Pattern (PNA), and Madden-Julian Oscillation (MJO), among others. Here is a brief description of a few that can affect our weather:

North Atlantic Oscillation (NAO) - Outside of El Niño, one of the primary influencers of winter weather in eastern North America and Europe is the NAO. A positive NAO occurs when atmospheric pressure over the high latitudes of the North Atlantic (i.e., Greenland) is below average and areas in the central North Atlantic have above average pressure. A strong jet stream across the eastern U.S. into the north Atlantic keeps the coldest winter air bottled up to the north, resulting in above average temperatures for the eastern U.S. A negative phase features above average pressure over the high latitudes and usually results in below normal temperatures and a snowy pattern for the eastern U.S. as cold air is allowed to dip into the region due to a weaker jet stream. The NAO can shift from positive to negative multiple times within a season or may vary in strength but remain in the same phase for several months at a time. At least through the early stages of the winter season, a positive NAO is expected.

The North Atlantic Oscillation (NAO) measures pressure anomalies over the North Atlantic Ocean. Higher than normal pressure over the northern latitudes of the north Atlantic typically results in a cold and snowy pattern for the eastern U.S. in winter. Graphic courtesy Climate.gov

Arctic Oscillation (AO) - A positive AO occurs when the ring of winds circulating around the polar region (commonly referred to as the "Polar Vortex") is strong, keeping cold weather confined to the highest latitudes around the North Pole. Higher pressure results in the mid-latitudes, along with less frequent intrusions of Arctic air. In a negative AO phase, this wind circulation weakens, allowing the cold polar air to penetrate south into the middle latitudes and increasing storminess in these areas as the polar jet stream dips south. This is what has been referred to in the media last January as the "Polar Vortex" invading the U.S., when in actuality, it is always there, just not always as far south. The AO is difficult to forecast more than a couple of weeks into the future.

The Arctic Oscillation (AO) measures anomalies in pressure in the Arctic region. A negative phase occurs with higher pressure at the north pole, resulting in intrusions of cold air into the mid latitudes. A positive phase occurs when the cold air stays bottled up at the pole, resulting in higher pressure in the mid latitudes. Graphic courtesy Climate.gov.

Pacific Decadal Oscillation (PDO) - As its name implies, this teleconnection generally lasts much longer (years at a time), varying in strength but generally staying in the same phase for long periods. The PDO is defined by ocean temperature anomalies in the northeast and tropical Pacific Ocean, with a positive phase occurring when warmer than average sea surface temperatures are positioned along the Pacific coast and cooler than average temperatures are located in the interior northern Pacific. After about 16 years in a negative phase, the PDO went positive about two years ago and remains that way now. It is a fairly recently-described concept and thus it effects are not yet well understood.

Pacific-North American Oscillation (PNA) - The PNA describes a pattern of mid-level pressure readings in distinct areas across the Pacific and North America. Usually, these pressure readings (or "heights") are similarly anomalous in the Aleutian Islands of Alaska and the southeast U.S. In the positive phase, heights are above average around Hawaii and in western North America and lower in the North Pacific and southeastern U.S. The positive phase tends to result in cooler and drier weather for the eastern portion of the country in the winter and also tends to occur during El Niño conditions, but not always.

Average temperatures during a strongly positive PNA regime in January 1981, courtesy of the State Climate Office of North Carolina. The country was virtually split in half with very cold air in the east and warmer than normal air in the west.

Madden-Julian Oscillation (MJO) - The MJO is an "eastward moving disturbance of clouds, rainfall, winds, and pressure that traverses the planet in the tropics and returns to its initial starting point in 30 to 60 days, on average" (Climate.gov). Because it is an intraseasonal tropical climate variable, it can change over the course of weeks. Its phase (of which there are eight) can have dramatic impacts on mid-latitude weather, including cold air outbreaks over the eastern U.S. in winter, flooding rain, and jet stream changes.

As you can see, the state of each of these teleconnections can alter or even reverse the impacts of a "typical" El Niño season for periods during the winter, which then affects the overall averages. It's important to remember that "climate is what we expect, weather is what we get." Thus there can be a difference between long-term, or seasonal, averages and day-to-day weather that makes up that average.

Winter outlooks from other sources

As I state every year, I am not an expert climatologist. At MWN, the focus is, nearly exclusively, on the short to mid-term forecasts - those out to a week to 10 days. So, as usual, in putting together our Mid-South winter outlook, I consulted multiple sources and researched data from winters past that I felt were comparable to what we might experience this year from a general pattern perspective (called analogs, listed at the end of the post).

Significant weight was given to previous winters that had strong El Niño conditions but consideration was also given to winters with weaker El Niños which had similar sea surface temperatures outside the Pacific ENSO region, namely the eastern north Pacific and western north Atlantic, since they would be most likely to have an effect on U.S. weather. In particular, I feel the warm waters near the Pacific coast and those in the north Atlantic will play more than a passing role in weather patterns over the U.S. and influencing the Mid-South.

The winter outlooks that I gave the most credence to were those from NOAA and WeatherBell Analytics, as their reasoning is sound and I generally agree with their premises of their respective outlooks, even though they differ slightly. You'll find those outlooks shown below.

NOAA Winter Outlook

NOAA's temperature outlook for this winter leans heavily on climatological expectations associated with El Niño. Percentages represent the likelihood of  above/below normal temperatures. In other words, there is a >40% chance that much of Texas will see cooler than normal weather this winter.

NOAA's precipitation outlook for this winter also leans towards El Niño climatology, though it depicts southern U.S wetness extending north into the southern Plains and Front Range, as well as up the east coast. Percentages are read similarly to the temperature map above. "Equal chances" means there is no signal to indicate a greater chance of above or below normal precipitation.

WeatherBell Winter Outlook

WeatherBell temperature forecast for the winter season. Colors represent departures from average.  In many respects, this outlook agrees with NOAA depicting a warm winter for the north and cool winter for the south.  The eastern 1/3 of the U.S. is where they differ the most.

The snowfall forecast for this winter from WeatherBell, expressed as percent of normal. Recall that for the south, where values are forecast well above average, snowfall amounts are typically not high, so a 150-200% of normal forecast could be only a few inches difference. NOAA does not expressly predict snowfall in their winter forecast. 

The MWN Winter Outlook

1. Temperature
All of that said, there is fairly strong consensus that Mid-South winter will start off warmer than it will end. In other words, the temperature anomalies will be positive (above normal) through December, then descend into negative (below normal) territory by February and March. In fact, the average temperature in December for the ten El Niño winters examined (analogs listed below) was 0.9° above normal while the average February temperature was 3.4° below normal. Thus I expect temperatures will be above normal, on average, through the end of the year before beginning to trend downward. Similar to last year, February and early March have the potential to be a fair amount below normal in the temperature arena.

2. Precipitation
Precipitation-wise, a warmer early season tends to support more atmospheric moisture than a cold season and our analog winters support that as well. By the time the latter half of the winter arrives, precipitation in the analogs falls below normal. In a classic El Niño setup, precipitation is usually near average in the Mid-South, but drier anomalies in the Ohio Valley can sometimes creep south into west and middle TN as well. Therefore, we are of the opinion that the winter will start off with above normal precipitation and the latter half of the season will be slightly below normal.  We also believe that severe weather activity will continue to be below average, which is fairly common in El Niño years.

3. Snowfall
The most anticipated part of the forecast, snowfall tends to be near the long-term average for the season, though it can be fairly variable. This is because one snow storm (or the lack thereof) can result in a season that is well above (or below) normal, since not much typically falls. (Memphis International Airport averages 3.4" of snow each year.) Last year, the December-February snow total was 2.3", or about an inch below normal. However, the first light accumulation actually occurred very early (0.1" in mid-November) and the biggest ice/snow event of the season actually occurred in the first week of  March, both outside the typical "winter" season. So for 2015-'16, we are predicting slightly above normal snowfall for the season (4-5") with the majority of that likely to occur later in the winter, not dissimilar to last year. With a forecast of cooler air in place in February to early March, we believe there is an above average probability of a late season snowfall in the Mid-South once again.

So there you have it - the predictions for 2015-'16 winter! If you're interested in how I did last year, take a look at this blog post from last March. In a nutshell, the winter of 2014-'15 was cold, dry and snowy. I had forecast temps below to slightly below average (correct), precipitation near average (incorrect), snowfall near to above average (correct), and large temperature swings with periods of severe weather (partially correct).

Footnote:
The analog years we examined for this year's outlook were 1919-20, 1957-58, 1972-73, 1982-83, 1991-92, 1994-95, 1997-98, 2002-03, 2009-10, and 2014-15. These included the 3 strongest El Niños on record (to this point): 1997-98, 1972-73, and 1982-83. Click here to view the raw data for each of these winters.

Erik Proseus
MWN Meteorologist

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El Niño, part I: The basics

With words like "Godzilla" and "strongest on record" being thrown around in relation to this winter's pending El Niño, you might be wondering just what El Niño is and what effects it will have on Mid-South weather. This is the first of a two-part blog series answering those exact questions.

In this installment, we'll answer the question "What is El Niño?" by putting the semi-technical terminology and atmospheric explanations on a shelf where you can reach it. In part 2, we'll look more closely at what the effects of El Niño conditions usually are globally and in our little corner of the world.

History of El Niño

El Niño traces its roots to a warming of the Pacific Ocean along the Ecuador/Peru coast in December, when the fishing season typically ends. El Niño literally means "The Little Boy" or "Christ child" in Spanish because the warming typically coincided with the Christmas season. Despite some annual warming, it was discovered that every few years the warming was more pronounced and coincided with heavy rainfall in typically dry coastal regions of Ecuador and Peru. Mid-20th century scientists discovered that the warming wasn't confined to the far eastern Atlantic, it actually spread across the eastern into the central Pacific near the Equator.

Link to the atmosphere

Further study in the 20th Century resulted in a discovery that the warming of the ocean water was also coupled with an atmospheric pressure oscillation called the Southern Oscillation. The oscillation of pressure results in changes in trade wind patterns (a prevailing pattern of surface winds blowing from the east found in the tropics) and rainfall distribution.

In "normal" conditions which are not El Niño or La Niña (commonly called "La Nada"), trade winds across the Pacific blow towards the west, causing warmer water near the surface of the ocean to be pushed westward. The temperature difference between cooler water to the east and warmer water in the west results in rising air over the western Pacific. This air evacuating the low levels of the atmosphere lowers the air pressure near the surface. In combination with warmer water that produces more evaporation in the same area, more clouds form and abundant rainfall occurs in the western Pacific. At the same time, in the east Pacific (off the coast of South America), atmospheric pressure is higher due to sinking air and rainfall is minimized.

Normal ("La Nada") conditions are shown above in a graphic from the Australian Bureau of Meteorology. Easterly trade wind pushes warmer water westward, resulting in lower pressure and increased precipitation over the west Pacific and cooler, drier conditions in the eastern Pacific.

In El Niño conditions, the trade wind weakens (or even reverses course in the strongest El Niños) and the warmer water shifts to the central and eastern Pacific, rather than the west Pacific. Rainfall patterns also shift, as rain tends to fall over warmer water for the reasons described above. Thus the normally-dry western coast of South America becomes wet and rainfall slacks off in the western Pacific. The shift in atmospheric heat, as a result of the displacement of warmer Pacific waters, disrupts atmospheric circulations globally, causing changes in weather and climate in places far removed from the Pacific Ocean, including across the United States.

El Niño conditions are shown above in another graphic from the Australian BOM. Easterly trade wind weakens, or even reverses, resulting in warmer water in the central and eastern Pacific and increased precipitation in the same regions. The western Pacific becomes drier with higher average pressure readings.

The ENSO Cycle

The complete name for El Niño is "El Niño/Southern Oscillation," or ENSO. The complete cycle from La Niña (the reverse condition of El Niño) to El Niño make up the "ENSO Cycle." El Niño episodes tend to occur every 2-7 years and typically last about 9-12 months. Much like a human being with a fever, there are varying degrees of El Niño and La Niña conditions, some relatively weak and others quite strong. It would follow that influences of ENSO can also vary widely, including the timing, duration, and intensity of the conditions.

How is ENSO measured? (this is a little more technical...)

The typical measurement that the National Oceanic and Atmospheric Administration (NOAA) uses to officially declare that El Niño conditions are occurring is based on sea surface temperatures (SST) in key areas of the equatorial Pacific, more specifically sea surface temperature anomalies (departure from normal). NOAA's Climate Prediction Center defines El Niño conditions as existing when three conditions are met:

• a one-month positive SST anomaly of 0.5°C or greater is observed in the Niño-3.4 region of the Pacific Ocean (see map below),
• an expectation that the 3-month Oceanic Niño Index (ONI, defined below) threshold will be met, and
• an atmospheric response typically associated with El Niño is observed over the equatorial Pacific

The Niño regions along the equatorial Pacific are shown above. Niño 3.4, which is the key region for declaration of an El Niño pattern, encompasses the central portions of the Niño 3 (in red) and Niño 4 (in yellow) regions.

The ONI is a running three-month average of SST anomalies for the key Niño 3.4 region. "Events" (El Niño or La Niña) are defined as five consecutive overlapping 3-month periods at or above the +0.5°C anomaly for warm (El Niño) events and at or below the -0.5°C anomaly for cold (La Niña) events. In other words, El Niño is not officially declared until five consecutive three-month averages are at least 0.5°C above normal, which happens seven months into an El Niño event, since running averages are used.

For example, ONI values over the past year (shown below) featured three consecutive three-month periods that met the 0.5°C threshold (from OND '14 through DJF '15), but fell short of official El Niño status when the JFM '15 anomaly was just below the 0.5°C threshold. However, since FMA '15, the Pacific has produced five consecutive ONI values at or above the 0.5°C threshold (in red below), including the most recent 1.7°C value. Thus, El Niño officially began in February 2015, but was not declared until the June-Aug. '15 average was calculated in early September.

Oceanic Niño Index (ONI) values since winter 2014. The past 7 three-month periods have equaled or exceeded 0.5°C. When 5 of these periods reach 0.5°C consecutively, an El Niño is declared by NOAA.

According to NOAA, El Niño conditions are expected to peak this winter and then decline heading into next spring and beyond, thus El Niño will be a major driver of weather and climate throughout the upcoming winter.

For more information on ENSO, see NOAA's Climate Prediction Center website, NOAA's El Niño Portal, or this page from the Pacific Marine Environment Laboratory.

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In the second part of this blog series, we will look more closely at 1) the effects of El Niño both globally and locally, 2) Mid-South weather in historical El Niños, and 3) what we expect from the weather this coming winter! Will it mean a colder or wetter winter? Find out here!

Erik Proseus
MWN Meteorologist

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El Nino ramps up - what it means to Mid-South weather

Climatologists and environmental scientists expected El Nino to appear over the winter of 2014-'15 and, though it never officially did, it appears it was only tardy, not absent. As we head into summer, NOAA has now indicated that a weak but strengthening El Nino is present and could become one of the strongest in quite some time later this year. In fact, NOAA is forecasting a higher than 80% chance that El Nino will continue through the remainder of the calendar year.

Sea surface temperature anomalies (departure from normal - orange to red above normal) increased over the past 3 months in the El Nino region from the west coast of South America into the central Pacific indicating a strengthening El Nino.

The various long-range computer models almost all support a strengthening El Nino this year with some indicating it could become very strong. 

El Nino's effects on winter weather are fairly well documented and understood (though local variations certainly exist and no two El Nino patterns are the same) but the effects in summer tend to be more muted and less predictable. There have also been many fewer instances of a strong summertime El Nino in recent decades, thus there are fewer cases to look back to and draw conclusions from.

So how will this summer's El Nino affect the Mid-South?

Dr. Jeff Masters, who writes on Weather Underground's Wunderblog, recently discussed the same topic and recounted the effects of two similar cases in particular, the summers of 1982 and 1997. Both of these summers were generally cool and wet across a large part of the continental U.S. Both of these summers were slightly below normal temperature-wise in the Mid-South as well.

El Nino also tends to bring wetter than normal conditions to the southern U.S. owing to a persistent subtropical jet stream. Masters indicates that "signals remain positive for widespread summer moisture." In fact, NOAA's June-August climate outlook shows the Mid-South on the eastern periphery of a large area of cool and wet conditions that they believe will dominate the central U.S. So, despite short-term trends that indicate a warmer-than-normal start to June, the summer average could end up a bit cooler (not to the exclusion of some periods of hot weather that we know are in store!).

The June-August temperature trends (left) as forecast by NOAA indicate a better than even chance of cooler than normal temperatures across the central U.S. with the western part of the Mid-South possibly cooler than normal. Precipitation-wise (right image), a large part of the Rockies, central, and southern U.S. could be wetter than normal, including the Mid-South.

It's also worth noting that there tends to be a marked decrease in Atlantic tropical activity during El Nino summers as well, owing to increased storm-destroying wind shear in the favored tropical formation regions. However, that could be partially offset by elevated sea surface temperatures (SSTs) in the Gulf of Mexico and Caribbean. So while the overall pattern could be quiet this year, it only takes one storm to feed on higher than normal SSTs near the U.S. to cause big problems for coastal residents. Tropical outlooks for 2015 that have been issued so far have indicated a below normal season. NOAA's Atlantic basin outlook, released  May 27, calls for a 70% chance of below normal activity due to El Nino. More specifically, NOAA predicts 6-11 named storms, 3-6 hurricanes, and up to 2 major hurricanes.

We'll see how the summer plays out - it will definitely be interesting to monitor!

Erik Proseus
MWN Meteorologist

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A pattern shift in the making

My apologies for having taken some time off from the blog after the recent Arctic outbreak. I guess I was thawing my fingers. The finger-thawing weather will continue for the foreseeable future, though with some temps in the 60s the past few days, I don't think there is any thawing left to be done!

While temps averaged over 15 degrees below normal for the first 10 days of January, highs have rebounded into the mid 50s to lower 60s the last 4 days and the forecast points to more of the same for at least the next week. Also of note, yesterday and today's rainfall of between 1.0-1.5" was the first rain of 2010, a full 16 days into January! Of course, we can't forget the few hundredths of an inch of liquid precip we picked up with the snow on January 7, but this was the first rain since December 31. This marks the latest "first rain day" to start a year in at least 15 years, which is how far my available records go back.

Looking ahead, following the Arctic intrusion that blanketed the eastern half of the nation to start the year, we are now in the midst of a "pattern shift" which will signal a significant change in U.S. weather patterns over the coming couple of weeks perhaps. During the first two weeks of January, the upper level pattern was marked by a large scale trough (upper level low pressure) over the eastern U.S. and a ridge over the west (upper level high pressure) (see graphic of the upper-level pattern on January 5, courtesy Storm Prediction Center, above).

Gradually that pattern has shifted to something more akin to El Nino years. We now will be seeing a flatter upper level pattern (lower amplitude troughs and ridges) with a strong jet stream pointed straight into the southwestern U.S. and northwestern Mexico (see graphic above valid mid-week; click for larger version). This pattern will mean frequent and strong storms for California, which will then move across the southern Rockies, southern Plains, and into the southeast U.S. More benign weather, outside of clipper systems from Canada, are expected across the northern tier of the U.S. So, if you are watching The Weather Channel or even national news, you'll definitely be seeing stories on the emergence of an El Nino weather pattern and probably flooding and mudslides in southern CA and feet upon feet of snow for the Sierra range. For more on the pattern shift and effects on our west coast neighbors, see Paul Yeager's excellent post "Storms to Blast California."

For the Mid-South, this will mean milder weather with storm systems approaching from the west or southwest that will bring rain every few days and perhaps setting the stage for one or more of these systems to bring the threat of some thunderstorms. The milder weather is due to the fact that these storms will be of Pacific origin and not Canadian origin. Between systems, with some sun, temperatures will have no problem reaching the 50s and 60s and overnight lows should remain "mild for January." More details will be found in the forecasts posted on MemphisWeather.net.

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It's beginning to look a lot like... El Nino!

Source: NOAA/CPC

The weather pattern over the Mid-South and southeastern U.S. is starting to take on a fairly typical "El Niño" look as we approach mid-week. The pattern is marked by progressive low pressure systems that emerge from the Desert Southwest into the western Gulf of Mexico on a fast-moving subtropical jet stream that zips over the southern tier of the U.S. They then tap into copious moisture from the Gulf, bringing torrential rains and the occasional chance of severe weather to the Gulf Coast. The lows then continues east or move northeast, depending on the track of the jet stream, sometimes continuing into the major metros of the Northeast U.S.

For the Mid-South, there are many factors that determine what results these western Gulf systems have on our weather. These include the exact track of the low itself, the amount of moisture it contains and the dynamics associated with the system, as well as the degree of cold air in place over the region, particularly in the lowest few thousand feet of the atmosphere. All of these factors make these systems some of the hardest to forecast for this region of the country, especially when cold air has to be factored in.

With respect to the upcoming system, which is already bringing flooding rains to the central Gulf coastal region and the possibility of severe weather to portions of the Gulf Coast and southeast, the low will likely track through the Tennessee Valley and up the spine of the Appalachians on Wednesday. (This track is somewhat atypical of a track for the classic El Niño storm, but it's origins are fairly El Niño-esque.) The low will be strengthening and there is plenty of moisture associated with it.

Fortunately, at least this time around, there just won't be enough cold air in place during the time the precipitation is falling to have to worry too much about the chance of anything but rain. For areas to the north of the metro, there is a small chance that sufficient cold air could seep in Wednesday night as the precipitation is ending to produce a few flurries. I do not expect this in the Memphis metropolitan region however, and there should be no accumulations anywhere in the Mid-South that flurries might fall thanks to warm ground temperatures during the very early stages of winter.

After this system passes us by, the coldest air of the season will set in, with temperatures falling below freezing Friday, Saturday, and probably Sunday mornings area-wide and highs Friday maybe struggling to reach 40 degrees! Saturday morning will be the coldest morning so far this winter with lows in the mid 20s likely in the city and maybe near 20 in outlying areas. Not good news for those running the St. Jude/Memphis Marathon or Half-Marathon on Saturday or attending one of many holiday events or parades around town this weekend!

Keep an eye on the MWN Forecast for the latest details on our first winter blast!

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Climate trends, El Nino, and waterfowl

I have seen several interesting weather items of note in the past couple of days that I thought I would touch on today. Here they are, in decreasing scale order (globally to locally):

October Climate Stats
While the U.S. experienced its wettest, and third coolest, October in recorded history, that didn't bear out across the rest of the globe. NCDC indicates, and Dr. Jeff Masters of Weather Underground reports, that last month was the 6th warmest October on record globally. In the U.S., temperatures averaged 4.0F below normal, while precipitation was almost double the typical October average. It appears from the graphic above that outside of the continental U.S., northern Europe was the only other region where temps averaged below normal. In addition, U.S. drought and fire activity both decreased in October.


El Nino Strengthens
According to the Climate Prediction Center's (CPC) weekly El Nino report issued this morning, El Nino conditions have strengthened across the central and eastern Pacific in the past month, with sea surface temperatures now averaging 1.0-2.0 degrees above normal. In fact, the most watched region of the Pacific (dubbed "El Nino 3.4") has now crossed a threshold that allows this El Nino event to be classified a "strong" event. Model forecasts call for moderate to strong El Nino conditions to continue through the 2009-2010 Northern Hemisphere winter. Three-month forecasts for the Mid-South reflect semi-typical El Nino considerations, including slightly below normal temperatures and below normal precipitation. More on the current El Nino conditions can be found here.


Another Winter Forecast
My blogosphere friend Paul Yeager of CloudyandCool.com wrote yesterday about a computer model called the NCEP coupled forecast system (CFS) that has advantages over typical day-to-day models in forecasting long-range (read Paul's blog for a great explanation). In the FWIW category, the CFS output agrees with the CPC and most other winter forecasts that have taken into consideration the effects of El Nino and forecasted cool and dry winter months for the Mid-South. For a look at U.S. temperature forecast maps from the CFS, click here, and for precipitation, click here.


Doppler Ducks
Ryan Vaughan with KAIT-TV in Jonesboro woke up Saturday morning to reports of large flocks of waterfowl (likely geese and some ducks) flying south over northeast AR. As he checked NWS Doppler Radar, he noticed what appeared to be light rain showers headed south over the area (while other returns were moving northeast through north MS). Putting two and two together, it was determined that the migratory birds were showing up on radar! (Read more on Ryan's blog, including a radar loop of the occurrence.)

While a very cool thing to witness, birds on radar is certainly not unprecedented (see my previous blog, "The Birds"). In fact, during certain times of year, at sunrise, "expanding donuts" of radar echoes appear near Reelfoot Lake and other areas around the region known to be excellent sleeping spots for our feathered friends. As the waterfowl take off in all directions, they show up as an ever-expanding ring of echoes.

So hunters, not only will checking the early morning forecast on MemphisWeather.net be helpful in determining the weather conditions for your stakeout, but accessing Doppler radar on MWN Mobile might net you a heads-up to an approaching flock!

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